Refrigeration control



June 5, 1945. c. G. KRONMILLER 2,377,503

REFRIGERATION CONTROL I Filed Dec. 20, 1940 2 Sheets-Sheet 2 Fig.4:

. INVENTOR darl G. Kronmillzr ATTORNEY Patented June 5, 1945REFRIGERATION CONTROL Carl G. Kronmiller, Minneapolis, Minn., assignorto Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., acorporation of Delaware Application December 20, 1940, Serial No.371,001

26 Claims.

This invention relates to a control mechanism for refrigeratingapparatus, particularly apparatus of the type employing a motor'drivencompressor.

In operating refrigerating apparatus of the compression type, adesirable sequence of operation is to start the compressor at atemperature of the evaporator high enough to indicate that theevaporator has defrosted and to stop it at a relatively low evaporatortemperature, the evaporator thus being defrosted after each cycle ofoperation of the compressor, This type of operation is disclosed in apatent of Charles B. Spangenberg No. 2,191,966.

The object of my invention is to provide an improved and inexpensiveswitching device for producingthe type of operation of a refrigerationsystem as disclosed in the above referred to patent.

More specifically the object of my invention is to provide a compact,inexpensive controller for refrigerating compressors using a minimum ofparts but still offering great freedom of adjustment and adaptability,the controller being responsive to both suction and head pressure of thecompressor.

A further object of my invention is to provide a compressor controllerfor producing the type of ing it in open position of the switch. Furtherobjects and advantages 'of my inven-- tion will become apparent from thefollowing detailed description and annexed drawings wherein:

Figure l is a diagrammatic representation of a refrigerating systemincluding a preferred form of the controller of my invention.

Figure 2 is a view of the interior of the controller of Figure 1, thatis, with the cover removed,

Figure 3is a detail view taken along line 3-4 of Figure 2.

Figure 4 is a view of the controller of Figures 1 and 2 as seen frombehind, this view being taken along line 4-4 of Figure 5.

Figure 5 is a view of the controller of Figure 4 taken along line 5-5.

Figure 6 is a view of a modified form of my invention.

Referring to Figure 1 of the drawings, numeral i0 designates acompressor of a conventional type refrigerating system.- The compressoris driven by an electric motor H by means of a. belt i2. The compressordischarges into a condenser l3 through a pipe l4 and the condenser isconnected to an expansion valve l5 by a pipe Hi. The expansion valve l5controls the admission of refrigerant to an evaporator l1 located withina chamber It, to be refrigerated. The outlet of the evaporator I1 isconnected to the suction side of the compressor ill by a pipe IS, Theexpansion valve I5 is of a type well known in the art wherein theexpansion of refrigerant into the evaporator is thermostaticallycontrolled. Numeral 22 designatesa bulb filled with an expansible fluidwhich is located adjacent to the outlet line or conduit of theevaporator H, The bulb 22 is connected by a capillary tube 23 to theexpansion valve IS. The manner of operation of expansion valves inrefrigeration systems of the type disclosed is well known in the art andneed not be described in detail.

The compressor motor I I is controlled by a controller 26, the detailsof which are more readily ascertainable from an inspection of Figure 2wherein the interior of the controller 26 is shown. The controller 26has a front cover 25 which may be suitably fastened to casing 21. InFigure 2 the controller is shown with the cover removed.

Referring to Figure 2, the controller 26 comprises a generallyrectangular casing 21 within which is a horizontal plate 28 forsupporting a snap-switch 29.. As will presently be described, thesnap-switch 29 is operated in response to suction pressur and headpressure of the compressor. Numeral 32 designates a housing whichencloses an expansible and contractible bellows, the interior of whichis connected to the suction line IQ of the compressor by a tube 33 (seeFigure 1). The housing 32 is flanged and the flange is secured to thelower part of the casing 21 by screws 34 and 35. Numeral 36 designates asimilar housing within which is an expansible and contractible bellows,the interior of which is connected to the discharge conduit of thecompressor by a tube 31 (see Figure 1). The housing 36 is flangedsimilarly to the housing 32 and the flange is attached to the lower partof the casing 21 by screws 39 and 40.

The screw 35 is relatively long and extends through a supportingstandard 4| for the plate 28 as shown. A similar'screw 42 extendsthrough another standard 43 lik the standard 4| which also serves tosupport the horizontal plate 28 as shown.

The snap-switch 29 is the same as the one disclosed in the applicationof Albert E. Baak Serial No. 307,991, filed on December 7, 1939. Thesnap-switch is enclosed within a Bakelite housing or casing 45 and haselectrical terminals formed by screws 46 and 41. The snap-switch 29 hasa Bakelite operating stem 48 extending below the casing of the switch.The snap-switch 29 is of a type wherein movement of the operating stem48 in an upward direction closes the switch and movement of theoperating stem 48 in a downward direction opens the switch. After theswitch has been operated to open or closed positions it tends to remainin that position.

Numerals 50 and designate wires connected to the terminal screws 46 and41 respectively. Wire 51 and another wire 52 are connected to a suitablesource of power and wires 59 and 52 are connected to the compressormotor as shown in Figure 1. Wires 58 and 5| extend through an opening incasing 21 as shown.

The moveable end of the bellows within housing 32 is connected to anoperating stem 55 which extends through a nut 54 as shown in Figure 2.The upper end of the stem 55 carries a ball member 56 which is disposedloosely within an opening in a floating operating lever 51. The left endof the operating lever 51 is disposed between two cams 58 and 59 and theopposite end of the operating lever 51. engages in a slot in theoperating stem 48 of the snap-switch. Numeral 68 designates a flexibleor resilient leaf attached to the upper side of the operating lever 51by rivets or the like, the leaf 60 engaging the ball 56. Numeral 6|designates a similar resilient leaf riveted to the lower side ofoperating lever 51, the leaf 6! having an opening through which theoperating stem extends and this leaf also engaging the ball 56. The ball56 and the resilient leaves 60 and GI form a strain release connectionbetween the operating stem 55 and the operating lever 51.

The cams 58 and 59 have. spiral contours as may best be seen on Figure3. The cam 58 is mounted on a shaft which is journaled in a side wall ofthe casing 21 and which may be rotated by a manual knob 65 exteriorly ofthe casing 21.

Adjacent to manual knob is a dial 66 which may be graduated if desired.The cam 59 is mounted on a similar shaft journaled in the side wall ofthe casing 21 and rotatable by a manual knob 51 exteriorly of the casing21. 61 is a dial 68 similar to the dial 66 which may also be graduatedif desired. The cams 58 and 59 form stops between which the left end ofthe operating lever 51 is moveable.

From the immediately foregoing it can be seen that when the bellowswithin housing 32 expands in response to rising suction pressure in thesuction conduit l9, the operating stem 55 is moved upwardly carrying theoperating lever 51 with it until the left end of lever 51 engages cam58. After the left end of lever 51 engages cam 58 further expansion ofthe bellows within housing 32 causes lever 51 to pivot about cam 58,that is, rotating in a counter-clockwise direction so that the right endof lever 51 moves operating stem 48 upwardly so as to close snap-switch29, closure of snap-switch 29 completing a circuit for the compressormotor through wires 51, 59 and 52. If the suction pressure shouldcontinue to rise after lever 51 is incapable of further movementAdjacent to knob the stem may continue to move upward slightly, the ball56 moving relatively to the lever 51 by flexing leaf away from the lever51, and thus relieving the strain on the operating mechanism of switch29.

Upon the suction pressure falling after the compressor motor is started,the bellows within housing 32 will contract drawing operating stem 55downwardly and causing the left end of lever 51 to be moved downwardlyuntil at a predetermined suction pressure it engages the cam '59. Uponfurther contraction of the bellows within housing 32, the lever 51 willpivot about cam 58, that is, moving in a clockwise direction so that itsright end moves the operating stem 48 of switch 29 downwardly so as toopen the switch 29 and thereby stop the compressor. Movement of theoperating stem 55 downwardly after the lever 51 is incapable of furtherdownward movement due to opening of the switch 29, the ball 56 will bemoved downwardly relative to the lever 51, the ball 55 flexing the leaf5| away from the lever 51. The resilient connections formed by theleaves 68 and SI thus prevent any strain from being placed upon theoperating connection between the stem 48 and the snap-switch 29.

From the foregoing it can readily be seen that the operatingdifferential of the snap-switch 29 in response to suction pressure isdetermined by the relative adjustment of the cams 58 and 59. If cam58'is rotated in a direction which would tend to move lever 51downwardly as seen on Figure 2, it is apparent that the pressure atwhich the switch is closed is lowered, because then the pressure willnot have to rise to as high value before lever 51 engages cam 58 andbegins to rotate in a counter-clockwise direction. If cam 59 is rotatedin the opposite direction obviously the suction pressure at which switch29 is closed will be raised. If cam 59 is rotated in a direction so asto decrease the space between the two cams the pressure at which switch29 is opened will be raised because obviously then the pressure will nothave to decrease to as low a value before lever 51 engages cam 59 andbegins to 1'0- tate in a clockwise direction. Obviously therefore, thedifferential of operation of the switch 29 can be adjusted by varyingthe positions of cams 58 and 59 by their respective manual knobs. It isalso apparent that the pressure at which the switch 29 is closed and thepressure at which it is opened can be independently adjusted.

The movable end of the bellows within the housing 36 is connected to anoperating stem 19 which extends through a nut 1|. The operating stem 10carries a screw member 12 which may be adjusted in a manner to adjustthe length of the stem 10 for a purpose which will be presently pointedout. Numeral 13 designates a bracket which is attached to the back ofthe casing 21 by a rivet or the like and which is rotatable a smallamount about its pivot. The bracket 13 carries a pivot 14 to which ispivoted an operating lever 15, the lever 15 having downwardly bent earswhich engage the pivot 14. The right end of the operating lever 15engages in a slot in the operating stem 48 of switch 29, this slot beingsimilar to the one in which the right end of lever 51 engages. The leftend of lever 15 is adjacent the upper end of operating stem 19, and whenthe discharge pressure of the compressor rises the operating stem 10 mayengage the lever 15 rotating it in a clockwise direction so that itsright end moves the operating stem 48 in a downward direction so as toopen the snapswitch 29. When the last mentioned operation occurs theright end of the lever 51 moves downwardly, the lever 51 movingrelatively to the ball 56 with the leaves 6! and 60 flexing if lever 51is engaging cam 58 at the time. Thus the strain release connectionbetween the operating stem 55 and the lever permits operation of thesnapswitch 29 in response to the head pressure bellows within thehousing 36. It should be noted that if the snap-switch 29 is opened inresponse to head pressure, the suction pressure must rise to apredetermined value to reclose the switch, this pressure value of coursebeing the one at which the switch is normally closed by suctionpressure. The switch cannot be closed by head pressure. The bracket 13has two extending fingers, as shown, between which is a small eccentric11. When the eccentric H is adjusted, the bracket 13 may be adjustedabout the rivet which attaches it to the back of the casing 21. Byadjusting the position of bracket 13, the position of pivot 14 relativeto the operating stem 19 and the operating stem 48 is adjusted. Thus the'movement of operating stem required for the operation of switch 29 maybe adjusted. By adjusting the screw member 1 I, the discharge pressureat which lever 15 will be operated to open switch 29 may be adjusted.

Figure 4 is a back view of the controller of -F ig ures 1 and 2 with thecover in place. The-cover carries a manual operating means which ispivoted to the cover and which is seen on Figure 4. The manual operatingmeans for the controller 26 comprises a manual lever 80, the left end ofwhich is bent into a U shape and which is carried on a pivot 8| as maybest be seen on Figure 5. The right end of the lever 80 has a bent overfinger 82 (see Figure l) which extends through a slot 83 in the cover ofthe instrument. The lever 80 has a projecting portion 85 carrying a pin86 as may be seen on Figures 4 and 5. Numeral 81 designates a pinextending inwardly from the cover of the controller and numeral 88designates a similar but slightly larger pin. Numeral 89 designates aflexible spr'ng element which is wound about the pin 88 and the ends ofwhich extend downwardly on opposite sides of the pins 86 and 81 adjacentthereto. Normally the lever 89 assumes an intermediate position in whichit is in as seen on Figures 1 and 4. ever the lever 80 is moved out ofthis position the pin 86 flexes either one or the other of thedownwardly extending ends of hte resilient element 89 which tends toreturn the lever 89 to its intermediate or normal position.

Numeral 90 designates a second shorter lever, the left end of which isbent into a U shape and which is carried on the pivot pin iii. The lever90 has a small bent over projection 9| and a longer projection 92 whichextends to a point adjacent to and above the operating lever 51. Numeral93 designates a resilient bracket member attached to the lever 88 andhaving a portion which extends outwardly to a position engaging theoperating stem 48 of the switch 29. Numeral 95 designates a small earbent over from the material adjacent slot 83. The finger 82 is adaptedto be latched in engagement with the car 95 as will presently bedescribed.

As shown on Figure 1 the finger 82 of lever 88 may have three positions.The intermediate position in which the lever 80 normally is, isdesignated on Figure 1 as automatic. When it is desired to manuallystart the compressor the lever 88 may be manually moved upwardly bymoving When i each cycle of operation.

the ear 82 upwardly'in slot 83 adjacent to the graduation marked start.When this is done the resilient bracket 93 by engaging the operatingstem 48 of switch 29 moves the stem upwardly moving the switch 29 toclosed position. As soon as the finger 82 is released the resilientspring element 89 returns the lever to the automatic position, that is,its intermediate position. If desired the snap-switch 29 may be manuallylatched in an off position so that the compressor cannot beautomatically started. To do this the operating manual lever 88 is moveddownwardly by moving the finger 82 downwardly in slot 83 to a positionbelow ear adjacent to the graduation marked off on Figure 1. The car 82may be latched or secured below the ear 95. When the manual lever 80 isthus moved downwardly the projection 92 engages the operating lever 51and moves its left end in a downward direction so as to move theoperating stem 48 of switch '39 downwardly to thus open the switch. Thestrain release mechanism associated with lever 51 as previouslydescribed permits downward movement of the left end if lever 57 isengaging cam 58 at the time. When the manual lever 86 is thus latched inits lowermost position, that is, in the off position, the compressorwill remain out of operation until the manual latch is released.Whenever the finger 82 is disengaged from the ear 95 the manual lever 88will be returned to its intermediate, that is, the automatic position inresponse to the resilient spring element 89.

From the foregoing description the complete operation of the system Ihave disclosed with the controller of my invention should be apparent.When the finger 82 is in the automatic position as shown on Figure 1 thecompressor will be started whenever the suction pressure rises to therelatively high value at which the snap-switch 29 is closed in themanner already described. The suction pressure at which the snap-switchcloses is normally set at a high enough value so that the evaporatorwill normally be defrosted after This operation corresponds to thatdisclosed in the patent referred to above. After having been started thecompressor remains in operation until the suction pressure falls to arelatively low value determined by the setting of cam 59 as describedabove. When this pressure is reached the snap-switch 29 is opened andthe compressor is stopped and thereafter the cycle will be repeated.Also as described above whenever the discharge pressure of thecompressor should rise to a relatively high value the operating stem 19will operate lever 75 to open the snapswitch 29 if it is closed at thetime. If the snapswitch 29 is open the discharge pressure responsivedevice may prevent it from being closed by the suction pressureresponsive device, the strain release arrangement permitting movement ofthe suction pressure below without movement of the switch.

As described above, the compressor may be manually started at any timeby manipulation of the finger 82 or the controller may be latched in itsoff position, also by manipulation of the finger 82 as described above.

Referring to Figure 6 of the drawings I have shown a slightly modifiedform of my invention. In this form of the invention the operating leverI51 on which the suction pressure responsive device acts is not made asa floating lever but is pivoted on a pivot I01. The left end of theoperating lever I5! is pivoted to a secondary lever I02, The left end ofthe lever I02 operates between the cams 58 and 59 which act as stops asin the previous embodiment and the right end of lever i02 engages theoperating stem 38 of the snap-switch 29 as in the previous embodiment.The head pressure responsive device acts on a lever 75 which engages theoperating stem 48 of the snap-switch 29 as in the previous embodiment.

In operation the device of Figure 6 operates very similarly to that ofthe previous embodiment. Upon a rise in suction pressure the operatinglever I51 is rotated in a clockwise direction about the pin NH and thesecondary lever I02 is rotated in a clockwise direction pivoting aboutthe slot in the operating stem 48 until its left end engages the cam 58.After the left end of lever I02 engages cam 58 the lever then pivotsabout cam 58 and is rotated in a counter-clockwise direction so that itsright end moves the operating stem 48 upwardly so as to close thesnap-switch 29. After the compressor has been started and the suctionpressure falls the suction pressure responsive device moves the leveri5! in'a counter-clockwise direction about pivot llii. This action moveslever I62 downwardly until its left end engages the cam 59. Furtherdownward movement of the left end of lever I5? causes lever N12 to berotated in a clockwise direction pivoting about the cam 59 with itsright end moving the operating stem 48 downwardly so as to open thesnapswitch 29. The head pressure responsive device may open switch 29 asin the previous embodiment.

From the foregoing it can be seen that the device of Figure 6 operatesvery similarly to that of the previous embodiment and that theadjustments of the closing and opening pressures of the snap-switch maybe made in the same manner.

From the foregoing it should be appreciated b those skilled in the artthat I have provided a very simple, inexpensive and useful device forcontrolling the compressor of a compression type refrigerating system soas to produce a sequence of operation whereby the evaporator isdefrostedafter each cycle of operation of the compressor. The controllerprovides for independent adjustment of the closing and opening pressuresof the switch and is entirely free from complex or delicate mechanismwhich might give rise to dimculties in use.

The embodiments of my invention which I have disclosed are illustrativeof its preferred form. There are many modifications which may be made bythose skilled in the art and there are many changes which readily fallwithin the realm and scope of my invention. The invention is not to belimited therefore by my disclosure but only by the scope of the claimsappended hereto.

I claim as my invention:

1. In a device of the class described, in combination, a switch, switchactuating means comprising a floating lever for operating the switch toboth of its positions, means forming stops between which the levermoves, means for moving the lever between said stops to actuate theswitch, and a separate automatic means for directly actuating the switchindependently of the lever.

2. In a device of the class described, in combination, switch meanshaving on and off positions and being of a type adapted to stay in theposition to which it is operated, actuating means for the switch meanscomprising a floating lever, means forming stops between which the leveroperates, means for actuating the lever, an automatic device foroperating said last means, and a manually operable member, said memberhaving means whereby when the member is moved in one direction theswitch is operated to one position and When the member is moved inanother direction the switch is operated to another position.

3. In a device of the class described, in combination, switch meanshaving on and oil positions and being of a type adapted to stay in theposition to which it is operated, actuating means for the switch meanscomprising a floating lever, means forming stops between which the leveroperates, means for actuating the lever, an automatic device foroperating said last means, a manually operable member, said memberhaving means whereby when the member is moved in one direction theswitch is operated to one position and when the member is moved inanother direction the switch is operated to another position, and meansfor latching said member so as to keep said switch in said otherposition.

4. In a device of the character described, in combination, a snap switchhaving open and closed positions and being of a type adapted to remainin the position to which it is operated, said switch having areciprocatable operating stem, a floating operating lever associatedwith said stem, stops between which said lever moves, a pivoted leverassociated with said floating lever and a device acting on said pivotedlever to move said floating lever between said stops for actuating saidstem and thereby operating the switch.

5. In a device of the character described, in combination, a snap switchhaving open and closed positions and being of a type adapted to remainin the position to which it is operated, said switch having areciprocatable operating stem, a floating operating lever associatedwith said stem, stops between which said lever moves and a device formoving said lever between said stops and actuating said stem so as tooperate the switch and a separate device for moving said stemirrespective of the position of said floating lever.

6. In a device oi the character described, in combination, a snap switchhaving open and closed positions and being of a type adapted to remainin the position to which it is operated, said switch having areciprocatable operating stem, a floating operating lever associatedwith said stem, stops between which said lever moves, a device formoving said lever between said stops and actuating said stem so as tooperate the switch and a separate device for moving said stemirrespective of the position of said floating lever, said last deviceincluding a pivoted lever associated with said stem and means wherebythe pivot of said last lever may be adjusted so as to vary the point atwhich said last device actuates the switch.

7. In a device of the class described, in combination, switch meanshaving on and off positions and being of a type adapted to stay in theposition to which it is operated, actuating means for the switch meanscomprising a floating lever, means forming stops between which the leveroperates, automatic advanceable and retractable means for actuating thelever, a manually operable member, said member having means whereby whenthe member is moved in one direction the switch is operated to oneposition and when the member is moved in another direction the switch isoperated to another position, means for latching said member so as tokeep said switch in said other position, and means normally biasing saidmember toward an intermediate position.

8. In a device or the character described, in combination, a switchhaving open and closed positions and being of a type adapted to stay inthe position to which it is operated, means including an operating leverfor said switch, a manually operable lever having an intermediateposition and means normally biasing said last lever so as to keep it insaid intermediate position, and said manually operable lever havingprojections adapted to engage said first "means for operating saidswitch when the manually operable lever is moved in either directionabout its pivot, said manually operable lever returning to itsintermediate position when released.

9. In a device of the character described, in combination, a switchhaving open and closed positions and being of a type adapted to stay inthe position to which it is operated, means including an operating leverfor said switch, a manually operable lever having an intermediateposition and means normally biasing said last lever so as to keep it insaid intermediate position, said manually operable lever havingproiections adapted to engage said first means for operating said switchwhen the manuallyoperable lever is moved in either direction about itspivot, said manually operable lever returning to its intermediateposition when released, and means for latching said manually operablelever in a position wherein said switch is closed.

10. In a device of the class described, in combination, a switch, switchactuating means comprising a floating lever for operating the switch,means forming stops between which the lever moves, means for moving thelever" between said stops to actuate the switch, and a separateautomatic means for actuating the switch independently of the lever, andmeans forming strain release connections between said lever and saidlever moving means.

11. In a device of the character described, in combination, a snapswitch having open and closed positions and being of a type adapted toremain in the position to which it is operated, said switch having areciprocatable operating stem, a floating operating lever associatedwith said stem, stops between which said lever moves, a device formoving said lever between said stops and actuating said stem so as tooperate the switch and a separate device for moving said stemirrespective of the position of said floating lever, and means formingstrain release connections between said first device and said lever.

12. In a device of the class described, in combination, switch meanshaving on and oil positions and being of a type adapted to stay in theposition to which it is operated, actuating means for the switch meanscomprising a floating lever, means forming stops between which the leveroperates, means for actuating the lever, a device for operating saidlast means, and a manually operable member, said member having meanswhereby when the member is moved in one direction the switch is operatedto one position and when the member is moved in another direction theswitch is operated to another position, and means forming strain releaseconnections between the device and the lever actuating means.

13. In a device of the class described, in com bination. switch meanshaving on and oii positions and being of a type adapted to stay in theposition to which it is operated, actuating means for the switch meanscomprising a floating lever, means forming stops between which the leveroperates, means for actuating the lever, a pressure responsive devicefor operating said last means at predetermined pressures, and a separatepressure actuated member for actuating said switch, said member being soconstructed and arranged as to be eifective to operate the switch to oneposition and ineffective to operate it to the other position whereby ifsaid member moves the switch to one position the pressure aifecting saidpressure responsive device must attain a predetermined value to move theswitch to the other position.

14. In a device of the character described, in combination, a twoposition switch of the type which tends to remain in either of its twopositions to which it is operated, a floating lever associated at oneend with said switch for causin operation thereof, a pair of stops forlimiting movement of the opposite end of said lever, said lever havingan opening at an intermediate portion thereof, a condition responsivedevice, a connecting rod associated at one end with said device andhaving an enlarged head at its opposite end fitting loosely within theopening in said lever, and resilient strain relief meanscarried by saidlever and tending to maintain the head of said connecting rod within theopening in said lever, but permitting relative movement therebetweenupon movement of said condition responsive device after further movementof said lever has been prevented.

15. In a device of the character described, in combination, a twoposition switch of the type which tends to remain in either of its twopositions to which it is operated, a floating lever associated at oneend with said switch for causing operation thereof, a pair of stops forlimiting movement of the opposite end of said lever, said level-havingan opening at an intermediate portion thereof, a condition responsivedevice, a connecting rod associated at one end with said device andhaving an enlarged head at its opposite end fitting loosely within theopening in said lever, resilient strain relief means carried by saidlever and tending to maintain the head of said connecting rod within theopening in said lever,

' but permitting relative movement therebetween value'of said condition,such action being permitted by said strain relief means.

16. In a device of the character described, in combination, a twoposition switch of the type which tends to remain in either of its twopositions to which it is operated, a floating lever associated at oneend with said switch for causing operation thereof, a pair of stops forlimiting movement of the opposite end of said lever, a first conditionresponsive device, means including a strain release connection betweensaid device and lever whereby the latter may be operated by the former,a second condition responsive device, a lever having a pivot, one end01' said lever being associated with said second condition responsivedevice. means connecting the other end of said lever to said switch foractuating the same, and means for adjusting the position of said pivotto vary the differential of operation of said switch by said secondcondition responsive device.

17. In a device of the character described comprising in combination, asnap action switch, an operator therefor, a condition responsive device,a pivotally mounted adjusting member, a lever, a

pivot for said lever carried by said member, one end of said lever beingoperatively associated with said condition responsive device, the otherend of said lever being associated with the operator for said switchwhereby said switch may be operated by said condition responsive device,and means for variably positioning said adjusting member and hence thepivot for said lever for varying the differential of operation of saidswitch.

18. in a control mechanism, in combination, a casing having an openingtherein allowing access to the casing, a control device within saidcasing, automatic means attached to said casin for operating saidcontrol device, a cover for closin the opening in said casing, andmanual operatin means for said control device comprising means carriedby and located inside of said cover but manually operable from theoutside thereof and which cooperates with said contro1 device when thecover is in place so that said control device is manually operable fromoutside said casing independently of said automatic means.

19. In a switching mechanism, in combination, a casing having an openingtherein allowing access to the casing, switching ,means within saidcasing, a floating lever in said casing for actuating said switchingmeans, automatic means carried by said casing for actuating saidfloating lever, an adjustable stop carried by said casing and having aportion within said casing engageable by said floating lever to causeactuation of said switching means upon actuation of said floating leverinto engagement with said stop by said automatic means, said adjustablestop having a portion outside of said casing by which it may beadjusted, a cover for the opening in said casing, and manually operablemeans for said switching means comprising means carried by and locatedinside of said cover but operable from outside said cover for operatingsaid switching means when said cover is in place.

20. In a switching mechanism, a two position switch of the type thatremains in the position to which it is operated and including areciprocable operating stem, a floating lever connected to said stem atone point on said lever, a condition responsive device acting upon saidlever at a second point removed from said second first point, and stopmeans cooperating with said lever at a third point, to cause movement ofsaid stem by said lever upon a predetermined movement of said lever bysaid condition responsive device.

21. In a control mechanism, in combination, a

casing having an opening therein allowing access to the casing, acontrol device within said casing, first automatic means attached tosaid casing for operating said control device, a second automatic meansattached to the casing for actuating the control device to itsinoperative position, a cover for closing the opening into the casing,and manual operating means for said control device including meanscarried by-and located inside of said cover but manually operable fromthe outside thereof and which cooperates with said control device whenthe cover is in place so that said control device is manually operablefrom outside the casing independently of said first and second automaticmeans, and means associated with the manual operating means inside thecover for holding the manual operating means in a predeterminedposition.

22. In a control mechanism, in combination,

a casing having an opening therein allowing access to the casing, acontrol device within said casing, automatic means attached to saidcasing for operating said control device, a cover for closing theopening in said casing, and additional means for controlling theoperation of said control device including means mounted on and lo-'cated within said cover arranged to provid such additional operationwhen said cover is in place on said control mechanism.

23. In a control mechanism, in combination, a casing having an openingtherein allowing access to the casing, a control device within saidcasing, automatic means attached to said casing for operating saidcontrol device, a cover for closing the opening in said casing,additional means for controlling the operation of said control deviceincluding means completely mounted on the inside of said cover arrangedto provide such additional operation when said cover is in place on saidcontrol mechanism independently of the automatic means, and means on thecover for maintaining the additional means in a predetermined position.

24. In a control mechanism, in combination, a casing having an openingtherein allowing access to the casing, a control device within saidcasing, automatic means attached to said casing for operating saidcontrol device, a cover for closing the opening in said casing, manualoperating means for said control device comprising means carried by andlocated inside of said cover but manually operable from the outsidethereof and which cooperates with said control device when the cover isin place so that said control device is manually operable from outsidesaid casing independently of said automatic means, and means associatedwith the manual operating means for automatically returning the manualoperating means to a predetermined position after the manual operatingmeans has been moved to a position for operating said control device.

25 In a control mechanism, in combination, a casing having an openingtherein allowing access to the casing, a control device within saidcasing, a cover for closing the opening in said casing, and means forcontrolling the operation of said control device including meanscompletely carried by the inside of said cover and arranged to provideoperation of the control device when said cover is in place on saidcontrol mechanism.

26. In a control mechanism, in combination, a casing having an openingtherein allowing access to the casing, a control device within saidcasing, automatic means attached to said casing for operating saidcontrol device, a cover for closing the openings in said casing, manualoperating means for said control device comprising means carried by andlocated inside of said cover, but manually operable from the outsidethereof and which cooperates with the control device when the cover isin place so that said control device ismanually operable from outside ofsaid casing independently of said automatic means, means for holding themanual operating means in ,a first predetermined position, and means forautomatically returning the manual operating means to a secondpredetermined position after said manual means has been moved to a thirdpredetermined position for operating said control device.

CARL G. KRONMILLER.

CERTIFICATE OF CORHECTLVION. 7 Patent no. 2,377,503. June 1915.

cums. KRONMILLER.

It is hereby certified that error appears in the printed specificationof the above numbered patent reqfiiring' correction as follows: Page 6,first column, line 149, claim 20, strike out the word "second"; and thatthe said Letters Patent 'shoald be read with this correction thereinthat the same may confom to the record of the case in the Patent Office.

Signed and sealed this 2nd day of October, A. D. 1915.

Leslie Frazer (Seal) First Assistant Comriissioner of Patents.

